1. Field of Invention
The present invention relates to a method and an electronic device for processing a digital image, and more particularly to a method and an electronic device for reducing digital image noises.
2. Related Art
In recent years, with significant development of digital technology and development of Internet and multimedia technologies, many images need to be converted into digital images for processing. The mode of directly capturing a real scene by using a digital camera, or capturing an image from a document or picture by using an optical scanner and then converting the image into digital image data for outputting has become a common method for obtaining digital images.
In order to meet requirements on image quality of users, various digital image processing techniques are developed to improve the quality of the digital images.
Among the image processing techniques, noise reduction and edge enhancement are quite important. As the high-frequency part in a signal is always weakened when an image is coded/compressed, image edges or other image details of the coded/compressed image are lost. However, the image processing method of noise reduction generally causes image blurring; while, on the contrary, the image processing method of edge enhancement generally leads to enhancement of undesired noises. It is difficult for the two image processing methods to reach a compromise.
Conventionally, noise reduction can be realized by averaging, suppression, blurring, or other means. However, as described above, the conventional methods fail to achieve balance between noise reduction and maintaining of image details. Therefore, the method of using a curve of an exponential function as the basis of noise reduction is introduced, which can achieve good balance between the two image processing methods.
However, the computation of reducing the image noises by using the exponential function is of high complexity, thus resulting in a low processing speed and excessively large consumption of computation resources. Besides, a large number of (possibly exceeding 100) multipliers and many adders/subtractors are required by the exponential function. The multipliers are of a high cost and occupy a large circuit space, so that the overall hardware cost is increased. In addition, in this method, an exponential function table is also needed to assist the computation, which further occupies the valuable memory space and again raises the cost.